Fuel-air ratio control for a reaction engine



March 12, 1963 D. E. CARR 3,080,708

FUEL-AIR RATIO CONTROL FOR A REACTION ENGINE Filed Sept. 14. 1960 2 SheetsSheet 1 THROTTLE COCKPIT SECTION INSTRUMENT AIR INVENTOR. Fla 3 D. E.CARR

A TTORNEYS March 12, 1963 D. E. CARR 3,08

FUEL-AIR RATIO CONTROL FOR A REACTION ENGINE Filed Sept. 14. 1960 2 sheets sheet 2 3 I l I c 1 R: I 2 2 I 1 1 I l I l r O I 1 l 4| so 100 I50 200 PERCENT OF STOICHIOMETRIC FUEL/AIR RATIO F IG. 5

FIG. 4

INVENTOR.

0. E. CARR A TTORNEYS 3,,7% Patented Mar. 12, 1963 3,086,708 FUEL-AIR PATH CQNTRGL FOR A REACIEON ENGINE Donald E. Carr, Bartlesville, Olden, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Sept. 14, 1960, Ser. No. 55,902 15 Claims. (Cl. oil-35.6)

This invention relates to combustion control in reaction motors. In one aspect this invention relates to preventing flame out in the combustion chamber of a reaction motor.

In reaction motors wherein a combustible mixture of a hydrocarbon fuel and an oxidant, such as air, is burned to produce combustion gases which are ejected rearwardly to obtain forward propulsive thrust, control of the combustion process is important in order to obtain high performance, properly protect the engin parts, and attain maximum eficiency commensurate with the performance desired from said motor or engine. Various methods and apparatus have been developed for controlling various aspects of the combustion process in such motors.

When reaction motors are employed in aircraft some difiiculty has been experienced with flame out, particularly at high altitudes. Flame out can occur when the fuel-air mixture becomes excessively rich during a period of rapid acceleration, such as when a fighter pilot desires to take evasive action. Flame out can also occur on the lean side, i.e., when the fuel-air mixture has been leaned out too much, such as when the pilot leans out the fuelair mixture in order to extend his range. Regardless of where the flame out occurs, i.e., on the rich mixture side or on the lean mixture side, it is obviously very important that flame outs be avoided if at all possible. The present invention provides a method and apparatus for preventing such flame outs.

It has been discovered that when hydrocarbon fuels are burned there are formed CH radicals and C radicals. The formation of said radicals does not fit into any accepted reaction mechanism of the combustion process, yet their presence in flame spectra has been well established. Said CH and said C radicals produce characteristic radiations in the wave length region of about 4300 and 5150 angstroms, respectively. It has also been discovered that the ratio R of the intensity of said radiations, designated I and 1 respectively, is a function of the fuel to air ratio in the combustion chamber; and further, that the value of R must be above about 0.5 to prevent rich mixture flame out and below about 3.5 to prevent lean mixture flame out.

Thus, broadly speaking, the present invention provides a method and apparatus for preventing flame out in the operation of a reaction motor; said method comprising measuring the ratio R of the intensity of the radiation produced by said CH radicals to the intensity of the radiation produced by said C radicals and controlling the fuel to air ratio in the combustion chamber of said motor in accordance with the value of R; and said apparatus comprising means for carrying out said method, either manually or automatically.

An object of this invention is to provide a method and apparatus for stabilizing the operation of reaction motors. Another object of this invention is to provide a method and apparatus for preventing rich mixture flame out during the operation of a reaction motor. Another object of this invention is to provide a method and apparatus for preventing lean mixture flame out during the operation of a reaction motor. Another object of this invention is to provide a method and apparatus for stabilizing the operation of a reaction motor between definite limits whereby both rich mixture and lean mixture flame out can be avoided. Still another object of this invention is to provide a methodand apparatus for preventing rich mixture flame out or lean mixture flame out by controlling the fuel to oxidant ratio in the combustion chamber of a reaction motor in accordance with the ratio R of the intensity of radiation produced by CH radicals to the intensity of radiation produced by C radicals, which radicals are formed during the combustion of a hydrocarbon fuel in the combustion chamber of said motor. Other aspects, objects and advantages of the invention will b apparent to those skilled in the art in view of this disclosure.

FIGURE 1 is a schematic view, partially in cross section, illustrating a turbojet engine provided with control apparatus which can be utilized for preventing flame out in accordance with the invention.

FIGURE 2 is a schematic view of a ram-jet engine illustrating how the control apparatus of FIGURE 1 can 'be employed in a ram-jet engine.

FIGURE 3 is a schematic view of a ram-jet engine illustrating how the air intake to said engine can be controlled in accordance with the invention.

FIGURE 4 is a schema-tic detailed view of one element of the apparatus of FIGURE 1.

FIGURE 5 is a graph further illustrating the relationship between the ratio R and the fuel to air ratio in the combustion chamber of a reaction motor.

Referring now to the drawings wherein like reference numerals have been employed to denote like elements, the invention will be more fully explained. It is to be understood that said drawings are schematic in nature. Many valves, pressure gauges, relays and other items of equipment not necessary for explaining the invention to those skilled in the art have been omitted so as to simplify said drawings. All of said individual apparatus elements shown in said drawings are commercially available conventional equipment. The present invention, insofar as the apparatus is concerned, resides in the various combinations and arrangements of said elements to obtain the improved results as described hereinafter.

In FIGURE 1 there is shown a schematic representation of a tur-bojet aircraft engine designated generally by the reference numeral 16. Said engine comprises a casing or housing 11 .of generally circular cross section having an air intake 12 and a discharge nozzle 13. Proceeding from the inlet end to the outlet end, casing 11 contains an air compressor 14-, a plurality of combustion chambers 16 arranged annularly around the engine at equally spaced intervals, and a gas turbine 17. Air compressed by said compressor 34- is used to support combustion of a liquid hydrocarbon fuel, such as kerosene or one of the l P type fuels such as JP-3, JP-4, etc., introduced into said combustion chambers through conduit 18 and nozzles 1?. The greatly increased volume of the resulting heated gases is fed through turbine 17 and thence outwardly through discharge nozzle 13. The purpose of turbine 17 is to drive said air compressor 14 by means of shaft 21 connecting the rotor assembly of said turbine with the rotor assembly of said compressor. Said turbine 17 includes a peripheral set of stationary blades 22 and a movable set of blades 23. Located centrally within the tailpipe of said engine is a dischar e air regulating plug 24 which is suspended therein by an appropriate structure not shown.

For the satisfactory operation of such a turbojet engine, the fuel to air ratio in the combustion chambers 16 must be controlled in order to attain high performance and prevent flame out. In accordance with the invention and to provide such control, at least one of said combustion chambers 16 is provided with a pair of adjacent spaced apart observation ports 26 for detecting the intensity of the radiations produced by the CH and C radicals formed during the combustion of the fuel. Said observation ports 26 and 26' are positioned so as to provide an sneer/es unobstructed view of the flame in said combustion chamber.

Referring to FIGURE 4 it will be seen that said observation ports 26 each comprises a sleeve 27 attached to and extending through the wall of said casing 11 and into said combustion chamber 16. A housing 28 is attached to the outer end of said sleeve 27. Said housing is provided with an opening in one side thereof which is in alignment with an opening 30 in the end of said sleeve 27. An optical filter 29 is fitted across said openings. Said optical filters are interference filters and are builtup sandwiches of vacuum deposited aluminum and alter-' nating layers of vacuum deposited dielectric material. Such filters can be purchased commercially for any desired range of wave lengths and one needs only to specify that one of the filters used in one of said observation ports 26 or 26 will transmit radiation within the range of 4200 to 4400 angstroms and that the other filter used in the other observation port will transmit radiation within the Wave length range of 5050 to 5250 angstroms. Thus, one of said observation ports will transmit only the radiation produced by said CH radicals in the region of about 4300 angstroms and the other of said observation ports will transmitonly radiation produced by said C radicals in the wave length region of about 5150 angstroms. Suitable optical filters of this type can be obtained from the Farrand Optical Company and are described in their bulletin No. 8. The radiation transmitted by each said optical filter activates a photocell 31 contained in the housing 28 in which the filter is positioned. Said photocells can be RCA type 926 photocells. Many other suitable types of detection devices sensitive to visible rays are commercially available and can be used in the place of the gas-filled vacuum tube type illustrated. For example, barrier layer type photocellscan be used.

The output signal from the photocell 31 in each of observation ports 26 and 26' are electrical signals and are fed to amplifiers 32 and 32' respectively. Said'signals are proportional to the intensity of the incident rays. Said amplifiers 32 and 32 can be any suitable type of D.C. amplifier. One suitable type is sold by the Electronic Associates Company as Type 6.112, described in their Bulletin AC-934. The signals from each of said amplifiers 32 and 32 is fed to an operational amplifier 33. Said operational amplifier is, in effect, a ratiometer. Several suitable amplifiers of this type for measuring current and voltage ratios are commercially available. One such commercially available instrument is described in Catalogue M-l90 (December 195 8) of the Electro Instrument Company, San Diegoll, California. 7

The electrical signal from said operational amplifier 33 is transmitted by means of lead 34 to transducer 36 which gauge can be utilized for hand control of said ratio R by the pilot if desired or necessary as explained further hereinafter.

Said transducer 36 and said. controller 38 are supplied with instrument air from conduit 42 from a source not shown. A pneumatic conduit 43 having a one-way check valve 44 therein extends from said controller 38 to a motor valve 45 disposed in said fuel inlet conduit 18. Another pneumatic conduit 47 extends from said controller 38 to port C of three-way valve 48 provided with ports A, B, and C. Said three-way valve is a spring loaded valve as shown and is normally biased to permit flow through ports A and B with port C being blocked.

A solenoid 49 is suitably mounted on the aircraft adjacent said three-Way valve 48 and the core rod of said solenoid 49 is operatively connected to the stem of said valve 48. A pair of electrical leads 51 extends from said solenoid 49 to a barometric or aneroid switch 52. Said switch 52 is of the type which is actuated by changes in barometric pressure and is normally open at the higher barometric pressures, such as exist at altitudes below about 25,000 feet, for example. A circuit 53 having a battery 54 therein connects said barometric switch 52 to manual switch 55 which is positionedin the cockpit of the aircraft and which can be operated manually by the pilot. Barometric switch 52. can be set or designed to close at any desired barometric pressure. Flame outs in reaction motors employed in aircraft rarely occur at altitudes of less than 20,000 to 25,000 feet; A pneumatic conduit 57 extends from port A of said three-way valve to air regulator 53. The pilots hand throttle 59 is operatively connected to said air regulator 53. Said air regulator 58 is supplied with instrument air from conduit 61.

The control apparatus of the invention provides means for effecting either automatic control or manual control of the fuel to air ratio in the combustion chamber of a reaction motor responsive to measurements of the ratio R of the intensity of the radiations produced by said CH radicals to the intensity of the radiation produced by said C radicals. Assuming it is desire-d to operate the aircraft and control the ratio R automatically at altitudes above 25,000 feet, switch 52 will be set to be normally open at altitudes of less than 25,000. feet. Under such conditions at altitudes of less than 25,000 feet the circuit from battery 54 supplying power to solenoid 49 will be open at. switch 52, said solenoid 49 will not be energized,

' and three-way valve 48 will be biased to its position perconverts said electrical signal to a pneumatic signal. Sev- 7 eral suitable transducers of a type suitableto be employed in the practice of the invention are available commercially. One such instrument is a Taylor 700T Elec trio/Pneumatic Transducer described in Bulletin 98262,

provides for remote control setting of the control index as described further hereinafter. Said controller is provided with proportional action plus reset action and limit 7 stops.

A gauge 39 is provided in'the cockpit of the aircraft; Said gauge 39 is an electrical gauge and isoperated by the electrical signal transmitted by lead 41 from said lead 34. Said gauge reads directly in l /l ratio, i.e., the ratio R, and is red lined atthetwo flame out points, i.e., 3.5 on the lean end and 0.5 'on the rich end. Said mitting flow through ports AB with port C leading to automatic controller 38 blocked. Under these conditions he aircraft will be under full manual control of the pilot. Movement of the throttle 59 will initiate a pneumatic signal from air regulator 58 which will pass through conduit 57, ports A-B of three-way valve 48, conduit 62, and conduit 44 to motor valve 46 which will thus be opened to admit fuel to spray nozzles 19.

When the aircraft reaches the altitude set on barometric switch 52 said switch will close, solenoid 49 will be ener' gized, and three-way valve 48 will be switched from its AB position to its A-C position permitting flow from air regulator 58 through conduit 57 and conduit 47 to controller 38. The pneumatic signal from the pilots throttle is then first fed into the pneumatic set accessory of said controller 38 and sets the control point of the controller. Said controller is provided with limit stops which are set at air pressures corresponding to the 0.5 and 3.5 values of the ratio R described above. 'Any attempt to move the throttle to a position which will result in a value of R outside the range of 0.5 to 3.5 .will not be effective. In other words, the throttle cannot be opened past the critical point which will result in a value of R of less than 0.5 on the rich mixture side, or closed past the critical point which will result in a value of'R of more than 3.5 on the lean side, when the aircraft is above the altitude set on said switch 52. Above s'aid'altitude setting of said switch 52, the pilot can fly the aircraft manually by means of said hand throttle 59' only between said two limit stops of 0.5 and 3.5. The pilot can watch gauge 39 in the cockpit and move the throttle to any desired setting which will give a control point in controller 38 between said limits of 0.5 and 3.5 For example, upon reaching cruising altitude the pilot can watch gauge 3? and decrease the fuel-air mixture to a level giving a control point approaching the limit of 3.5 for cruising. Once this control point has been set on the controller, said controller will maintain the ratio R at the value chosen by the pilot. This provides automatic control of the ratio R. If for any reason the pilot should find it necessary to deviate from these cruising conditions, such as increasing or decreasing the fuel to increase or decrease speed, the controller upon movement of the throttle will set a new control point between said two limit stops 0.5 and 3.5.

If for any reason the pilot desires to operate the aircraft entirely by manual operation, he can open switch 56 which will break the circuit supplying power to solenoid 49. Regardless of the altitude of the aircraft, threeway valve .8 will be immediately biased to its AB position and the aircraft will be on manual control. When said switch 56 is closed suchmanual control occurs automatically when the aircraft descends to altitudes of less than 25,000 feet because, as explained above, switch 52 will open at these lower altitudes.

The above described control apparatus of the invention provides a number of advantages in addition to the main advantage of being able to prevent flame out by controlling the fuel to air ratio in the combustion chamber in accordance with the value of the ratio R. For example, below 25,000 feet, or some other selected altitude setting, the aircraft is controlled manually by the pilots throttle in the normal manner. Thus, the aircraft is under normal manual control at both take off and landing. However, when the aircraft is on automatic control the pilot cannot vary the fuel to air ratio to such values that the limits of 0.5 and 3.5 on the ratio R will be exceeded.

Another advantage of this control system is that the pilot can watch gauge 39 and if there should be any mechanical failure in the central system such that it increases or decreases the fuel to air ratio to values where the ratio R approaches one of said limits 0.5 or 3.5, the pilot can then open switch 56 whereupon said solenoid will be de-energized and three-way valve 48 will be auto matically biased to its AB position and put the aircraft on hand control. Said three-way valve 48 could of course be provided for manual control only in which case the pilot would set said valve for control through the controller after he reached an altitude above which flame out is normally encountered. However, such a manual system is fallible since the element of human judgment is involved. The barometric switch 52 and its associated circuit is much preferred because it is more foolproof. Switch 56 is provided for emergency use only.

In FIGURE 2 there is illustrated diagrammatically one modification of a ram-jet aircraft engine. Said ramjet aircraft engine can also be controlled in accordance with the invention. In the ram-jet engine of FIGURE 2, designated generally by the reference numeral 70, atmospheric air enters casing 71 of the engine through air intake openings '72 located between said casing 71 and air diffuser 73 positioned in said air intake or opening 72. Air entering said engine passes rearwardly past fuel nozzles 74 located annularly about air difluser 73. The resulting fuel-air mixture then passes into combustion chamber 76 from which combustion gases produced by the combustion of said fuel are discharged from the engine through exit nozzle 77. Since in a ram-jet engine large quantities of fuel must be burned efliciently in a small space without excessive pressure drop, flame holders such as 78 are provided. These flame holders, as shown, are in the form of V-shaped rings mounted within casing 1 of said engine. Within said V-shaped rings the velocity of the fuel-air mixture is extremely low so that combustion readily takes place in this region, thereby reducing the chance of blow out should the flow velocity entering combustion chamber 76 change. Thus, combustion generally takes place in the region designated by reference numeral 76. While said flame holders '78 serve to stabilize combustion in the engine to a remarkable degree, the danger of flame out is still present. To avoid these flame outs the control apparatus associated with turbojet engine 10 in FIGURE 1 can also be employed with the ram-jet engine of FIGURE 2 in the same manner as described above in connection with FIGURE 1.

In FIGURE 3 there is shown a second ram-jet engine similar in construction to the engine shown in FIGURE 2 and having like parts designated by like reference numerals. Those parts of the control apparatus bearing the same reference numerals as in FIGURE 1 perform the same function in the control of the engine of FIGURE 3. However, in FIGURE 3 the fuel-air ratio in combustion chamber 76 is controlled by varying the air input to said engine rather than by varying the fuel input. This correction is accomplished by moving diffuser 73' longitudinally with respect to engine casing 71 so as to vary the size of the air intake opening 72. Suitable means for accomplishing this movement include servomechanism 77 actuated by the output of amplifier 78, the input of which comprises electrical voltage fluctuations from controller 79 which in turn is actuated by the signals received from amplifier 33, the operation of which is the same as de scribed above in connection with FIGURE 1. Servomechanism 77 drives lever 81 by means of worm gears 82, said lever 81 being hinged at pivot 83 on engine casing 71 and secured to said air diffuser 73 through rods 84 and 86. Rotation of lever 81 about pivot 83 adjusts the longitudinal position of diffuser 73 within air intake 72, thereby increasing or decreasing the size of said air intake 72 as may be required to properly adjust the fuelair ratio in combustion chamber 76 in accordance with the measurement of ratio R so as to maintain said ratio R within said limits of 0.5 and 3.5.

Any suitable type of controller can be employed as controller '79. One suitable instrument is a Swartout Autronic Controller Type A 60 as described in Bulletin A-702 (1958) of the Swartout Company, 18511 Euclid Avenue, Cleveland 12, Ohio. Any suitable type of servomechanism can be employed. For example, servomechanism 77 can be of the type shown in Electronic Control Handbook, Batcher and Moulick, page 298, Caldwell- Clements, Inc., New York, New York, 1946.

The operation of a reaction motor in accordance with the practice of the invention is further illustrated by reference to FIGURE 5. In this figure there is shown the relationship between the value of R as previously defined and the fuel to air ratio. In said FIGURE 5 the fuel to air ratio is expressed as the percent of stoichiometric fuel to air ratio. By stoichiometric ratio there is meant the weight ratio just required to supply suflicient oxygen to burn the fuel completely to carbon dioxide and water. For many hydrocarbon fuels the stoichiometric weight ratio of fuel to air falls in a range between about 0.5 and 0.30. Generally, the fuel to air weight ratio is kept between about 0.7 to about 1.5 times the stoichiometric ratio. At cruising conditions the jet engine is operated with a slightly lean mixture so as to obtain maximum utilization of the fuel so as to increase range. Fuelrich mixtures are sometimes employed to reduce flame temperatures and provide a reducing atmosphere to minimize corrosion of engine hardware (turbine blades, etc.).

The curve of FIGURE 5 illustrates the results obtained when measurements are made to determine the relationship between said ratio R and the fuel to air ratio. For lean mixtures, when operating a turbojet engine on a hydrocarbon fuel such as kerosene, the value of said ratio R is generally greater than 1.0 and is commonly between l.0 and 2.5. As the richness of the mixture is increased the value of said ratio R decreases. If one continues to increase the richness of the mixture, a limiting value of the ratio R will be reached at which flame out will occur. In FIGURE this limiting value of R has a value of about 0.5 and occurs at a fuel to air ratio of about 160 percent of stoichiometric. This blow out ratio is indicated by the dotted line connecting the abscissa and the curve. In the practice of the invention, the controller is set to avoid iiame out. Thus, in the operation of the engine according to the invention, as the value of R decreases or increases toward the danger point, for example about 0.7 on the rich mixture side and about 3.2 on the lean mixture side, the controller functions to decrease or increase the ratio of fuel to air and thereby increase or decrease the value of R, as the case may be. As explained above, the controller can be set to regulate the value of R between desired limits, e.g., at a value within the range of about 1 to 3. In the manner the engine can be controlled to operate at good fuel efficiency even though the load on the engine may vary, and yet'the danger of flame outs can be avoided.

While the above control system has been described as a pneumatic control system, it would be a simple matter for one skilled in the art in possession of this disclosure to convert said system to a hydraulic system or even to an electrical system.

Also, while the invention has been described primarily as using air as the oxidant for the hydrocarbon fuel, it V will be clear to those skilled in the art that it is within the scope of the invention to use other oxidants, for example, such as pure oxygen or ozone. V

7 From the above description it is believed it should be apparent that there has been provided in accordance with this invention a method and an apparatus for avoiding flame out in the operation of reaction motors. The'control mechanism of the invention can be utilized in various forms to accomplish the method of the invention so as to prevent said flame outs.

, While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto. Various other modifications will be apparent to those skilled in the art in view of this disclosure. Such modifications are within the spirit and scope of the invention.

7 I claim:

1. In the operation of a reaction motor wherein a combustible mixture of a hydrocarbon fuel and an oxidant is burned in a combustion zone of said motor with the formation of CH radicals which produce a characteristic visible radiation and C radicals which produce a different characteristic visible radiation, the method of preventing flame out in said combustion zone, which method comprises: detecting the intensity of the radiation produced by said CH radicals; detecting the intensity of the radiation producedby said C radicals; measuring the ratio R of the intensity of the radiation produced by said CH radicals to theintensity of the radiation produced by said C radicals; and controlling the fuel to oxidant ratio in said combustion zone in accordance with said ratio R.

2. A method for preventing flame out in a combustion zone of a jet engine wherein a combustible mixture of a hydrocarbon fuel and air is being burned, which method comprises: detecting the intensity of visible radiation within. the range of 4200 to 4400 angstroms; detecting the intensity of visible radiation within the range of 5050' to 5250 angstroms; measuring the ratio R of the intensity of visible radiation within the range of 4200 to 4400 angstroms to the intensity of visible radiation within the range of 5050 to 5250 angstroms; and controlling the fuel to air ratio in said combustion zone in accordance with :the value'of said ratio R. V 3. The method of claim 2 wherein said fuel to air ratio is controlled to maintain said ratio R within the range of about 0.5 to about 3.5. a V

1 4. The method of claim 3 wherein said fuel to air ratio is controlled by varying the amount of fuel admitted to said combustion Zone.

5. The method of claim 3 wherein said fuel to air ratio is controlled by varying the amount of air admitted to said combustion zone.

6. A method for stabilizing combustion and preventing flame out in 'a combustion zone of a turbojet aircraft engine wherein a combustible mixture of a hydrocarbon fuel and air is being burned, which method comprises: detecting the intensity of visible radiation within the range of 4200 to 4400 angstroms; detectin the intensity of visible radiation within the range of 5050 to 5250 angstroms; measuring the ratio R of the intensity of visible radiations within the range of 4200 to 4400 angstroms to the intensity of visible radiations within the range of 5050 to 5250 angstroms; and maintaining said ratio R within the range of about 0.5 to about 3.5 by varying the fuel to air ratio in said combustion zone responsive to said measurement of said ratio R.

7. The method of claim 6 wherein said aircraft engine is a ram-jet engine.

8. The combination, with a reaction motor having a combustion chamber wherein a combustible mixture of a hydrocarbon fuel and an oxidant is burned with the formation of CH radicals producing a characteristic radia' tion and C radicals producing a different characteristic radiation, of means for detecting the intensity of the radiation produced by said CH radicals, means for detecting the intensity of the radiation produced by said C radicals,

cans for measuring the ratio R of the intensity of the radiation produced by said CH radicals to the intensity of the radiation produced by said C radicals, and means for controlling the fuel to oxidant ratio in said'combustion chamber responsive to said measurement of said ratio R.

9. Apparatus for preventing flame out in a combustion chamber of a jet engine wherein a combustible inixtureof a hydrocarbon fuel and air is being burned with the formation of a flame producing radiations over a widerange of the visible spectrum, said apparatus comprising: means for detecting the intensity of said radiations within the range of 4200 to 4400 angstroms; means for detecting the intensity of said radiations within the range of 5050' to 5250 angstroms; means for measuring the ratio R of said intensities of said ranges of radiations; and means for controlling the fuel to air ratio in said combustion chamber responsive to said measurement of said ratio R.

10; In a turbojet aircraft engineincluding an air con.- pressor, a combustion chamber positioned rearwardly of said compressor and receiving air from said compressor, a gas turbine position rearwardly of said combustion chamber and adapted to be driven by heated gases from said combustion chamber, 'a drive shaft connecting said compressor to said turbine, and fuel inlet means for injecting a hydrocarbon fuel into said combustion chamber wherein a combustible mixture of said fuel and air are burned with the formation of CH radicals which produce a characteristicradiation and C radicals which pro- .duce a different characteristic radiation; apparatus for preventing flame out in said combustion chamber, comprising in combination: means positioned in a wall of said combustion chamber for detecting the intensity of said radiationproduced by said CH radicals; means positioned in said wall of said combustion chamber for detecting the intensity of said'radiation produced by said C radicals;

"l'fiiiO in said combustion chamber and maintain said ratio 7 R within the range of about 0.5 to about 3.5.

ll. In a turbojet aircraft engine including an air compressor, a combustion chamber positioned'rearwardiy of said compressor and receiving air from said compressor,

a gas turbine positioned rearwardly of said combustion chamber and adapted to be driven by heated gases from said combustion chamber, a drive shaft connecting said compressor to said turbine, and fuel inlet means for injecting a hydrocarbon fuel into said combustion chamber wherein a combustible mixture of said fuel and air are burned wtih the formation of a flame producing visible radiations over a wide range of the visible spectrum; apparatus for preventing flame out in said combustion chamber, comprising, in combination: means positioned in a wall of said combustion chamber for detecting the intensity of said radiations within the range of 4200 to 4400 angstroms; means postioned in said wall of said combustion chamber for detecting the intensity of said radiations within the range of 5050 to 5250 angstroms; means operatively connected to both of said detecting means for measuring the ratio R of the intensity of said radiations within the range of 4200 to 4400 angstroms to the intensity of said radiations within the range of 5050 to 5250 angstroms; and means responsive to said measurement of said ratio R for regulating said fuel inlet means to control the fuel to air ratio in said combustion chamber and maintain said ratio R within the range of about 0.5 to about 3.5.

12. In a ram-jet engine which includes an air intake, an air intake diffuser positioned in said air intake, 21 flame holder positioned rearwardly of said diffuser, a combustion chamber positioned rearwardly from said flame holder, a discharge nozzle positioned rearwardly of said combustion chamber, and fuel inlet means for injecting a hydrocarbon fuel forwardly of said flame holder into a stream of air admitted through said air intake to form a combustible mixture of said fuel and air which is burned in said combustion chamber with the formation of, CH radicals which produce a characteristic radiation and C radicals which produce a different characteristic radiation; apparatus for preventing flame out in said combustion chamber, comprising, in combination: means positioned in a wall of said combustion chamber for detecting the intensity of said radiation produced by said CH radicals; means positioned in said wall of said combustion chamber for detecting the intensity of said radiation produced by said C radicals; means operat-ively connected to both of said detecting means for measuring the ratio R of the intensity of said radiation produced by said CH radicals to the intensity of said radiation produced by said C radicals; and means responsive to said measurement of said ratio R for regulating said fuel inlet means to control the fuel to air ratio in said combustion chamber and maintain said ratio R within the range of about 0.5 to about 3.5.

'13. In a ram-jet engine which includes an air intake, an air intake diffuser positioned in said air intake, a flame holder positioned rearwardly of said diffuser, a combustion chamber positioned rearwardly from said flame holder, a discharge nozzle positioned rearwardly of said combustion chamber, and fuel inlet means for injecting a hydrocarbon fuel forwardly of said flame holder into a stream of air admitted through said air intake to form a combustible mixture of said fuel and air which is burned in said combustion chamber with the formation of a flame producing visible radiations over a wide range of the visible spectrum; apparatus for preventing flame out in said combustion chamber, comprising, in combination: means positioned in a wall of said combustion chamber for detecting the intensity of said radiations within the range of 4200 to 4400 angstroms; means positioned in said wall of said combustion chamber for detecting the intensity of said radiations within the range of 5050 to 5250 angstroms; means operatively connected to both of said detecting means for measuring the ratio R of the intensity of said radiations within the range of 4200 to 4400 angstroms to the intensity of said radiations within 10 the range of 5050 to 5250 angstroms; and means responsive to said measurement of said ratio R for regulating said fuel inlet means to control the fuel to air ratio in said combustion chamber and maintain said ratio R within the range of about 0.5 to about 3.5.

14. In a ram-jet engine which includes an air intake, an air intake diffuser positioned in said air intake, a flame holder positioned rearwardly of said diffuser, a combustion chamber positioned rearwardly from said flame holder, a discharge nozzle positioned rearwardly of said combustion chamber, and fuel inlet means for injecting a hydrocarbon fuel forwardly of said flame holder into a stream of air admitted through said air intake to form a combustible mixture of said fuel and air which is burned in said combustion chamber with the formation of CH radicals which produce a characteristic radiation and C radicals which produce a different characteristic radiation; apparatus for preventing flame out in said combustion chamber, comprising, in combination: means positioned in a wall of said combustion chamber for detecting the intensity of said radiation produced by said CH radicals; means positioned in said wall of said combustion chamber for detecting the intensity of said radiation produced by said C radicals; means operatively connected to both of said detecting means for measuring the ratio R of the intensity of said radiation produced by said CH radicals to the intensity of said radiation produced by said C radicals; and means responsive to said measurement of said ratio R for regulating the position of said air intake diffuser in said air intake to control the fuel to air ratio in said combustion chamber and maintain said ratio R within the range of about 0.5 to about 3.5.

15. In a ram-jet engine which includes an air intake, an air intake diffuser positioned in said air intake, a flame holder positioned rearwardly of said diffuser, a combustion chamber positioned rearwardly from said flame holder, a discharge nozzle positioned rearwardly of said combustion chamber, and fuel inlet means for injecting a hydrocarbon fuel forwardly of said flame holder into a stream of air admitted through said air intake to form a combustible mixture of said fuel and air which is burned in said combustion chamber with the formation of a flame producing visible radiations over a wide range of the visible spectrum; apparatus for preventing flame out in said combustion chamber, comprising, in combination: means positioned in a wall of said combustion chamber for detecting the intensity of said radiations within the range of 4200 to 4400 angstroms; means positioned in said Wall of said combustion chamber for detecting the intensity of said radiations Within the range of 5050 to 5250 angstroms; means operatively connected to both of said detecting means for measuring the ratio R of the intensity of said radiations within the range of 4200 to 4400* angstroms to the intensity of said radiations within the range of 5050 to 5250 angstroms; and means responsive to said measurement of said ratio R for regulating the position of said air intake diffuser in said air intake to control the fuel to air ratio in said combustion chamber and maintain said ratio R within the range of about 0.5 to about 3.5.

References Cite in the file of this patent UNITED STATES PATENTS 2,360,166 Schumann Oct. 10', 1944 2,589,971 Skarstrom Mar. 18, 1952 2,799,136 De Boisblanc Iuly 16, 1957 OTHER REFERENCES Spectroscopic Studies of Low-Pressure Flames, Gaydon et al.; Third Symposium on Combustion and Flame and Explosion Phenomena; Waverly Press Inc., Baltimore, Maryland, 1949; pages 504-518 (page 505 relied on). 

8. THE COMBINATION, WITH A REACTION MOTOR HAVING A COMBUSTION CHAMBER WHEREIN A COMBUSTIBLE MIXTURE OF A HYDROCARBON FUEL AND AN OXIDANT IS BURNED WITH THE FORMATION OF CH RADICALS PRODUCING A CHARACTERISTIC RADIATION AND C2 RADICALS PRODUCING A DIFFERENT CHARACTERISTIC RADIATION, OF MEANS FOR DETECTING THE INTENSITY OF THE RADIATION PRODUCED BY SAID CH RADICALS, MEANS FOR DETECTING THE INTENSITY OF THE RADIATION PROPOSED BY SAID C2 RADICALS, MEANS FOR MEASURING THE RATIO R OF THE INTENSITY OF THE RADIATION PRODUCED BY SAID CH RADICALS TO THE INTENSITY OF THE RADIATION PRODUCED BY SAID C2 RADICALS, AND MEANS FOR CONTROLLING THE FUEL TO OXIDANT RATIO IN SAID COMBUSTION CHAMBER RESPONSIVE TO SAID MEASUREMENT OF SAID RATIO R. 